CAN’T ANSWER. LOVE TOO MANY.
The obvious choice is Garrus, because he’s my Space Boyfriend. He’s a good character, though, regardless of the space boyfriend choice or not. He’s loyal to a fault, and while it DOES come back to be a fault more often than not, it’s a character trait that makes him interesting and a good balance to Shepard no matter what she’s doing.
I also love Mordin, though, because he’s a hero in every sense of the word, with surprising character growth and just good feels.
And I have love for Kasumi, simply because she’s awesome and gets the best loyalty quest in 2.